The =scapula= forms a long curved flattened bone expanded at its anterior end, where it meets the coracoid, and lying across the ribs at its tapering posterior end. It helps to form the imperfect =glenoid cavity=, with which the humerus articulates. The =coracoid=, a shorter but stouter bone than the scapula, has its upper end or =head= thickened and bears on its posterior border an irregular surface, with part of which the scapula articulates, while the rest forms part of the glenoid cavity. The inner border of the coracoid adjoining the articular facet for the scapula is produced into a strong process which helps to complete the =foramen triosseum=, a space lying between the adjoining ends of the scapula and coracoid, through which the tendon of the second pectoral muscle passes. The lower part of the coracoid, which is much flattened and expanded, and abruptly truncated posteriorly, articulates with the coracoid groove of the sternum. The _clavicle_ is a thickened curved membrane bone, which is fused with its fellow in the middle line below, the two forming the _furcula_ or merrythought. Its dorsal end is drawn out into a process which articulates with the coracoid. THE ANTERIOR LIMB OR WING. This consists of three parts, a proximal part, the upper arm or =brachium=, a middle part, the fore-arm or =antibrachium=, and a distal part, the =manus=. When extended for flight the parts lie almost in the same straight line, but when at rest they are folded on one another in the form of a Z, the brachium and manus pointing backwards, and the antibrachium forwards. When extended for flight the surfaces and borders of the wing correspond in position with those of the primitive vertebrate limb[104], the pre-axial border being directed forwards and the postaxial backwards, while the dorsal and ventral surfaces look respectively upwards and downwards. But when the wing is at rest, the humerus as it extends backwards becomes slightly rotated, so that its dorsal surface looks more inwards than upwards, while the dorsal surface of the antibrachium looks partially outwards and upwards, and that of the manus mainly outwards. The =brachium= or =upper arm= contains only a single bone, the =humerus= (fig. 57, 1). This is a large nearly straight bone expanded at both ends. The proximal end is specially expanded, forming two =tuberosities=, and a large convex =head= articulating with the glenoid cavity. The =pre-axial tuberosity= is the smaller of the two, but is continued by a prominent =deltoid ridge=, which extends for a very short distance down the shaft. The =postaxial tuberosity= is the larger, and below it there is a very deep pit, the =pneumatic foramen=, which leads into an air cavity in the shaft of the bone. The shaft is long and straight, and at the distal end of the bone is the =trochlea= with two convex surfaces, one pre-axial with which the radius articulates, the other postaxial for the ulna.